056 FXUS63 KMPX 080405 AFDMPX Area Forecast Discussion National Weather Service Twin Cities/Chanhassen MN 1105 PM CDT Tue Jul 7 2020 .Updated for 06Z Aviation Discussion... Issued at 1102 PM CDT Tue Jul 7 2020 && .SHORT TERM...(This evening through Wednesday night) Issued at 302 PM CDT Tue Jul 7 2020 Surface analysis this afternoon shows a west-east oriented cold front sitting over the I-90 corridor over SD-MN-WI, then curling northeast to its main low pressure center over Hudson Bay. It also transitions to a warm front over central Montana. Aloft, a weak shortwave disturbance is moving across WI and away from the area while a small broad ridge from the deep South up to the Dakotas approaches from the west. A longwave trough sits over far western NOAM. After isolated morning convection in association with the exiting shortwave trough, the incoming ridge has capped off the atmosphere sufficiently and will maintain itself this evening through the overnight hours. This will prevent any additional showers/thunderstorms from impacting the WFO MPX coverage area for the rest of the day today and through the overnight hours. Afternoon cumulus development will diminish with the loss of daytime heating, just allowing for passing high clouds overnight. However, the ridge axis aloft will shift to the east tomorrow while the next organized frontal system pushes through the Dakotas and will move into western MN by late day tomorrow. Its warm front is expected to lift north through southern-central MN and western WI during the day, effectively placing the coverage area within the warm sector of the arriving system. With an eroding cap and the longwave trough shifting east, stronger southwesterly low level flow within the warm unstable warm sector will contribute to much more instability by mid- to-late Wednesday afternoon. As capping erodes by late day, thunderstorms will initiate upstream in the Dakotas and move east southeast across the area during the evening into early morning hours Wednesday and Wednesday night. Some of the storms may become strong to severe with large hail and damaging winds, as alluded to in the SPC Day 2 Outlook. Coverage/duration is highly uncertain, which has been reflected in the CAMs the past several days, but given the larger-scale scenario with the frontal positions and falling heights with the exiting ridge, having pops into the "likely" range is certainly viable. The other concern for Wednesday is the heat. With highs surging into the lower 90s for much of southern MN into western WI, and potentially as high as 94-96 degrees, and dewpoints reaching the lower 70s for much of the coverage area, this will push heat index values to near 100 for much of southern-eastern MN into western WI. Confidence is high enough in this thinking to issue a Heat Advisory for southern-eastern MN and portions of western WI, including the entire Twin Cities metro (for heat index values there of 95-100 degrees). .LONG TERM...(Thursday through Tuesday) Issued at 302 PM CDT Tue Jul 7 2020 Adjusted PoPs lower across portions of west and central Minnesota on Thursday as dry westerly flow settles in behind the cold front. Kept higher PoPs across southern MN and west-central Wisconsin as the boundary will linger and influence showers through Thursday afternoon. Friday looks to dry out in between shortwaves, but another shortwave trough tops the ridge over the SW CONUS. There are still some model differences regarding the placement of the forcing so I've opted to retain the higher NBM PoPs on Saturday until there is better confidence. The zonal flow should provide some minor relief from the tropical- like dew points this weekend. Temperatures will remain in the mid to upper 80s and dew points in the lower 60s. This relief will be short lived as guidance builds the SW CONUS ridge toward the Plains and the heat/humidity will return to the Upper Midwest next week. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1102 PM CDT Tue Jul 7 2020 VFR conditions throughout. Could be a few spots of patchy fog, but southeasterly winds should increase and keep it from getting too widespread so did not include mention in the TAFs. Thunderstorms are expected to develop later Wednesday afternoon at KRWF KAXN and KSTC and could affect the other sites in the evening and overnight. KMSP... Mainly VFR conditions throughout, but thunderstorms are expected to develop later Wednesday afternoon out west and could affect KMSP during the evening. The precipitation has trended slow, so pushed back the timing in the TAFs. /OUTLOOK FOR KMSP/ Thu...Mainly VFR with TSRA/MVFR early. Wind SW 5-10 kts. Fri...VFR. Wind NW 5 kts. Sat...Mainly VFR. Chance TSRA/MVFR. Wind W to NW 5 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...Heat Advisory from noon to 7 PM CDT Wednesday for WIZ023>028. MN...Heat Advisory from noon to 7 PM CDT Wednesday for MNZ059>063- 066>070-075>078-083>085-092-093. && $$ SHORT TERM...JPC LONG TERM...BPH AVIATION...JRB